Fig 1: Identifying Pressure Regulator

Courtesy of SAAB-SCANIA OF AMERICA, INC.

The pressure regulator is mounted on the short side of the fuel rail.

The pressure regulator maintains a constant ratio between the fuel pressure and the pressure in the intake manifold. This ensures that the amount of fuel injected is determined exclusively by the opening duration of the electromagnetic injectors.

The pressure regulator is a diaphragm-controlled overflow valve set for 3.0 bar. The regulator consists of a metal housing divided into two chambers by a press-fitted diaphragm. In one of the chambers a spiral spring presses against the diaphragm while fuel flows through the other chamber.

When the preset pressure is exceeded, a valve controlled by the diaphragm exposes an opening to the return line through which superfluous fuel can flow back to the fuel tank.

The spring-loaded chamber of the pressure regulator is connected by a hose to the engine's intake manifold after the throttle. In consequence, the pressure in the fuel system is affected by the absolute pressure in the intake manifold, with the result that the pressure drop across the injectors is constant at all intake manifold pressures.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Pressure regulator

Use the Manual With the Right Hardware

When to See a Mechanic